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Category - Soils

Soil Test Interpretation Guide

 
Element Nitrogen
(N-NO3)		 Phosphorus (P)   Potassium (K)

Extraction
Method

  2N KCl Bray Olsen Ammoniun Acetate Ammonium Bicarbonate - DTPA
Rating ppm ppm ppm meq/100g ppm ppm
Low <20 <20 <15 <0.45 <175 <60
Adequate 20-41 20-40 15-25 0.45-0.7 175-280 61-120
High 41-75 40-100 >25 0.7-2.0 280-800 121-180
Excessive >75 >100 >2.0 >800 >180

 

  
Element Calcium (Ca) Magnesium (Mg) Sulfur
(S-SO4)

Extraction

Method

 Ammonium Acetate Ammonium Acetate KCL 40
Rating meq/100g ppm meq/100g ppm ppm
Low <5 <1000 <0.5 <60 <5
Adequate 5-10 1000-2000 0.5-1.5 60-180 5-10
High >10 >2000 >1.5 >180 10-20
Excessive >20

 

 

  
Element Iron (Fe) Manganese (Mn) Zinc (Zn) Copper  (Cu) Boron (B)
Extraction
Method		 DTPA DTPA DTPA DTPA Hot Water
Rating ppm ppm ppm ppm ppm
Low <2.5 <0.6 <1.0 <0.6 <0.5
Adequate 2.5-5.0 >2.0 >1.5 >2.0 0.5-2.0
High >5.0 >2.0

 

 

 

  
Interpretation of Soil Electrical Conductivity
Rating 1:1 Extract EC (mmhos/cm) Saturated Paste
ECe (mmhos/cm)
Low (Non-saline) 0.01-0.45 0.0-2.0
Low (Slightly saline) 0.45-1.5 2.1-4.0

Medium (Moderately saline)

 1.51-2.9 4.01-8.0
High (Strongly saline) 2.91-8.5 8.01-16.0
Very high (Very strongly saline) >8.5 >16.0

 

 

 

Desirable range of exchangeable cations
Cation Range
Calcium 65%-80%
Magnesium 10%-20%
Potassium 3%-8%
Sodium <6%
Aluminium <1%




Remarks:

 

  • Tests represent availability index and do not measure the actual amount insoil,  but only the fraction extracted by the specific extraction method. 
  • The values and ranges presented are in no way absolute. The aim is for you to use this document to get better understanding of the numbers and the terms used in soil test reports.